Current networks bear multiple services, such as voice, video, online gaming, and Web browsing. In recent years, a lot of large telecom operators choose the GPON (Gigabit Passive Optical Network, gigabit passive optical network) as a solution as future large bandwidth optical access, thereby imposing higher requirements upon metropolitan area network devices, that is, requiring these MAN devices to be able to interconnect with the GPON. With the use of large-capacity optical digital communication transmission systems and the introduction of various new services, communication networks become more complex and have larger capacity. This requires the metropolitan area network devices to support TDM (Time Division Multiplexing) services and multiple type data interfaces according to features such as diversified data service types and uncertain traffic.
In the prior art, a method for transmitting multiple services based on dynamic bandwidth adjustment is provided, and mainly applied on a ring network. On a ring network, the nodes are classified into N nodes and S nodes. The N node refers to a normal discrete service access node, and the S node, also called the master node, has the functions of the N node and can interconnect with upper-layer networks. Any node can directly add and drop conventional services such as TDM and Ethernet data services, and can also provide PON (Passive Optical Network, passive optical network) branch interfaces. The S node provides 10 GE (Gigabit Ethernet, gigabit Ethernet) uplink service interfaces. The services borne on the ring network includes three type: (1) fixed bandwidth services, referred to as FB (Fixed Bandwidth), mainly used to bear services with assured bandwidth and delay, for example, TDM, SDH (Synchronous Digital Hierarchy, synchronous digital hierarchy)/SONET (Synchronous Optical Network, synchronous optical network), and private line services; (2) assured bandwidth services, referred to as AB (Assured Bandwidth) services, for example, video, VoIP (Voice Over Internet Protocol, voice over Internet Protocol), and private line services; (3) best effort services, referred to BE (Best Effort) services, for example, ordinary Internet access services. For the AB and BE services, the network is a convergence network. The convergence node is the S node, and the node implements dual backup. For the FB services, the network is a peer-to-peer switching network on which TDM, SDH/SONET, and private line services can be added or dropped at any node.
The network includes three layers: a service adaptation layer, a channel layer, and a physical layer, the architecture is simple, the circuit processing is simple, and the reliability is high. Therefore, the cost is saved, and the power consumption is reduced, and the implement is easy. The service adaptation layer is responsible for encapsulating and decapsulating various services according to the format of an E-GEM (Enhanced GPON Encapsulation Method, enhanced GPON encapsulation method) frame and specifying a unique identifier for each service on the network. According to the principles such as service type, priority, and destination address, the channel layer adds channel overheads to multiple E-GEM frames to compose different types of T-CONT (Transmission Container, transmission container) frames, that is, channel layer frames. In this way, the end-to-end alarm and transmission performance monitoring can be implemented at the channel layer. The physical layer combines all the T-CONT frames into a TC (Transmission Convergence, transmission convergence) frame, that is, a physical layer frame, and adds physical layer overheads, including frame header synchronization, management overheads and a bandwidth map, to the TC frame to form a GTH (Generic Transport Hierarchy, generic transport hierarch) frame. In this way, the master node on the network can manage and communicate with each N node, so that it convenient to adjust the allocated timeslots of each TCONT, and dynamic bandwidth adjustment is implemented.
The process of implementing DEA (Dynamic Bandwidth Assignment, dynamic bandwidth assignment) by the network is as follows. Each N node detects, and take statistics on the DBR (Dynamic Bandwidth Requirement, dynamic bandwidth requirement) information of each service port on the node, and reports the DBR information to the master node; the master node performs judgment and calculation according to the current bandwidth resources on the ring, service types of each node, and priority, and delivers bandwidth assignment information of each node to each node; and each node transmits data according to the assigned bandwidth. The bandwidth assignment information refers to the BWmap (Bandwidth Map, bandwidth map). The size and number of T-CONT frames assembled by each node depends on the bandwidth map.
The prior art has at least following disadvantages.
If the bandwidth map of a working channel is the same as that of a protection channel, when any node sends services to the working channel and the protection channel respectively, delay may occur due to the alignment of the frame headers in both the channels. When the bandwidth map of the working channel is different from that of the protection channel, services can only be sent to the working channel and cannot be sent to the protection channel because the time sequence of the working channel is different from that of the protection channel.
As a result, the dual-transmission process fails. When lines of different rates are multiplexed, the time sequences cannot be aligned due to the mismatch of rates. In this case, services on low-rate lines can be mapped to high-rate lines only after being cached for a certain period of time, which causes delay and cache problems. For the FB services, due to the feature of a constant time sequence, after one or some TC frames are deleted, bandwidth map fragments may occur. Consequently, DBA dynamic assignment on the bandwidth map fragments is complex, and is difficult to be implemented.